Device and method for forming coating layer

Abstract

A device for forming a coating layer on a member surface according to the present invention is characterized by comprising: a preheating part that preheats a filler material composed of a hard alloy having a rod shape to a softening temperature; a heat source that applies heat for forming a molten pool on the member surface; and a feeding part that feeds the preheated filler material to the molten pool, the filler material being fed in a softened state without being melted until fed into the molten pool. A method for forming a coating layer on a member surface according to the present invention comprises: providing a filler material composed of a hard alloy having a rod shape; softening the filler material composed of the hard alloy having the rod-shape; heating the member surface and forming a molten pool on the member surface; and feeding the filler material in a softened state without melting the filler material until fed into the molten pool.

Description

Coating layer forming device and method

[0001] The present invention relates to an apparatus and method for forming a coating layer, particularly a hard alloy coating layer. This application claims priority from Japanese Patent Application No. 2023-222106, filed on December 28, 2023. The entire contents of said Japanese Patent Application are hereby incorporated by reference.

[0002] Powder metallurgy is a method for producing components using hard alloys. In this method, hard alloy powder is pressure-molded into a shape with a cutting allowance relative to the shape of the target component, sintered, and then the sintered body is processed by grinding, electric discharge machining, etc. to obtain the shape of the target structural component.

[0003] In this method, because a cutting allowance is provided, there are portions that do not become the target component, to varying degrees, resulting in waste of expensive raw material powder containing W, Co, and Ni. Also, hard alloys are used in portions that do not actually require the use of hard alloys, resulting in waste of expensive raw material powder. Therefore, several proposals have been made in light of this situation.

[0004] For example, Patent Document 1 describes a method for producing a sintered body of a complex shape using an additive manufacturing method, which is said to be capable of obtaining a sintered body of a shape very close to the desired shape and to reduce the amount of raw material powder used.

[0005] Furthermore, for example, Patent Document 2 describes a cutting tool that uses a hard alloy only in necessary portions, and describes a composite member having an intermediate layer between a cemented carbide part made of a WC-Co based cemented carbide and a member part containing 50 mass % or more of Ni and Co in total, and it is said that the composite member has excellent high-temperature strength and can suppress the occurrence of cracking and peeling.

[0006] JP 2018-83959 A International Patent Publication No. 2019 / 069701

[0007] The present invention aims to provide an apparatus and method for forming a hard alloy coating layer, which can produce a highly durable coating layer having a sound alloy structure (defined below) without wasting expensive W, Co, or Ni powders.

[0008] The apparatus for forming the hard alloy coating layer is as follows.

[0009] An apparatus for forming a coating layer on a surface of a component, comprising: a preheating section for preheating a rod-shaped filler metal made of a hard alloy to a softening temperature; a heat source for applying heat to form a molten pool on the surface of the component; and a feeding section for feeding the preheated filler metal into the molten pool, wherein the filler metal is fed in a softened state without being melted until it is fed into the molten pool.

[0010] The apparatus for forming the coating layer may also satisfy the following (1), or (1) and (2), or (1), (2) and (3), or (1) and (4), or (1), (2) and (4).

[0011] (1) The feed section includes a roll, and the roll is located between an outlet of the preheating section and above the molten pool. (2) The roll has a pressing section that applies a pressing force to the softened filler metal in a direction perpendicular to the surface of the member. (3) The feed section further includes a second roll. (4) The member has at least one surface layer, and the molten pool is formed in the at least one surface layer.

[0012] The method for forming the hard alloy coating layer is as follows.

[0013] A method for forming a coating layer on a surface of a component, comprising: providing a rod-shaped filler metal made of a hard alloy; softening the rod-shaped filler metal made of a hard alloy; heating the surface of the component to form a molten pool on the surface of the component; and feeding the filler metal in a softened state without melting it until it is fed into the molten pool.

[0014] The method for forming the coating layer may satisfy the following (5), or (6), or (7), or (5) and (7), or (6) and (7).

[0015] (5) The rod-shaped hard alloy filler metal is fed into the molten pool while applying a pressure to the filler metal, (6) the pressure is applied by a roll, and (7) the member has at least one surface layer.

[0016] The hard alloy coating layer formed by the coating device and the forming method has a sound alloy structure due to a low area ratio of abnormal phases and voids, and the component has high durability. Furthermore, since the hard alloy coating layer is formed only on the surface (for example, in areas of the component where hardness and mechanical strength are more important), the use of raw material powders containing expensive W, Co, and Ni can be reduced.

[0017] 1 is a schematic diagram of an example of an apparatus for forming a coating layer of hard alloy according to one embodiment of the present invention, FIG. 2 is a schematic diagram of an example of an apparatus for forming a coating layer of hard alloy according to another embodiment of the present invention, and FIG. 3 is a schematic diagram of an example of a die cutter which is a member having a surface coating layer of an example.

[0018] The present inventor first studied the disclosures of Patent Documents 1 and 2 to find a way to increase the durability of cutting edges (cutting edge shaped portions) and forming grooves in, for example, cutting tools, cutting tools, coating devices, and die rolls having forming grooves (collectively referred to as tools) using a small amount of raw material powder containing expensive W, Co, and Ni, and confirmed the following points.

[0019] (1) Regarding the additive manufacturing method described in Patent Document 1, voids exist between the granulated powder particles, and because pressure molding using a press or other method is not performed, voids (cavities) remain in the sintered body heated by a laser. One method for suppressing voids in the sintered body is to increase the laser output and melt the granulated powder at a high temperature. However, when granulated powder of a hard alloy containing a hard phase and a binder phase is melted at a high temperature, the high-melting-point hard phase melts, generating an embrittlement phase or a hard phase with grain growth. This prevents the formation of a sound alloy structure (defined below), resulting in a decrease in the hardness and strength of the molded body. Furthermore, this additive manufacturing method is difficult to use to manufacture large components.

[0020] (2) Regarding the cutting tool described in Patent Document 2, in which a hard alloy is used only in necessary portions, Patent Document 2 describes that cracking and peeling are suppressed by forming an intermediate layer in which the components of the hard alloy and the component are mixed. However, since the hard alloy, which is composed of a high-melting-point hard phase and a low-melting-point binder phase, is melted by direct irradiation with a heat source, the intermediate layer does not have a sound alloy structure. Furthermore, the component is limited to Ni, Co, or an alloy containing a total of 50 mass% or more of Ni or Co, making it difficult to manufacture a hard alloy composite structure in which steel is used as the component.

[0021] Next, the following known techniques were examined, and the following findings were reached: (3) Wire Directional Energy Deposition (DED) Method The wire DED method is a method in which a filler metal in wire form is fed, melted by a laser to coat a component, and finished into a desired shape. However, because it is difficult to control the temperature of the filler metal when heating with a laser, when the filler metal is a hard alloy, the hard phase also melts, resulting in the formation of an embrittlement phase or a hard phase with abnormal grain growth in the coating layer, which reduces the hardness and strength of the component on which the coating layer is provided.

[0022] (4) Overlay welding Overlay welding is a process in which both the surface of a workpiece and the tip of a wire-shaped filler metal are melted by a heat source to form a molten pool on the surface of the workpiece, and the filler metal is fed into the molten pool from a direction different from the heat source to form the surface of the workpiece with the filler metal. However, in this type of overlay welding, if a hard alloy is used as the filler metal, the coating layer will not have a sound alloy structure.

[0023] Based on this understanding, the inventors conducted further research and found that if the filler metal is in the form of a rod rather than a wire, and is heated to a temperature that softens the filler metal without melting it using a preheating section such as electrical heating, and then the workpiece is fed into a molten pool that has been melted using a heat source separate from the preheating section, such as a laser, electron beam, plasma, or arc, and the filler metal is heated in the molten pool without melting the hard phase of the hard alloy, then a coating layer formed on the workpiece using the hard alloy filler metal can have a sound alloy structure. The present invention is based on this finding.

[0024] The wire shape refers to a wire rod that is easily bent so that it can be fed from a cylindrical body such as a bobbin, whereas the rod shape refers to a wire rod that is highly rigid and difficult to bend, making it difficult to feed from the cylindrical body. The rod shape may have any cross section, such as a circle, an ellipse, or a rectangle.

[0025] Hereinafter, an apparatus and a method for forming a hard alloy coating layer according to an embodiment of the present invention will be described. In this specification and claims, when a numerical range is expressed as "L to M" (L and M are both numerical values), this is synonymous with "not less than L and not more than M," and the range includes an upper limit (M) and a lower limit (L). When a unit is stated only for the upper limit, the upper limit (M) and the lower limit (L) have the same unit.

[0026] The term "hard alloy" as used in the claims and this specification refers to an alloy (super hard alloy) based on W carbide or any of the carbides, nitrides, and carbonitrides of elements in Groups 4 to 6 of the periodic table, and further containing iron group elements such as Co and Ni.

[0027] In this specification, "sound alloy structure" refers to a structure that does not contain (a specified proportion or less) defects such as embrittlement phases, low carbon phases, free carbon phases, and coarse hard phases (these phases and defects are collectively referred to as abnormal phases), nor voids (not to be distinguished from voids). Furthermore, "the appearance of the coating layer is normal" refers to the absence of cracks, overlaps, humping, undercuts, or meandering when the coating layer is visually inspected.

[0028] 1. Rod-shaped hard alloy filler metal The rod-shaped hard alloy filler metal will be described.

[0029] (1) Composition The rod-shaped hard alloy becomes the hard alloy coating layer and is fed as a filler metal. There are no particular restrictions on the composition, but examples include the following:

[0030] 1) WC cemented carbide Co: 5.0 to 20.0 mass%, Cr: 2.0 mass% or less (including 0.0 mass%), V: 1.0 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities. Preferably, Co: 7.0 to 10.0 mass%, Cr: 1.5 mass% or less (including 0.0 mass%), V: 0.5 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities. More preferably, Co: 10.0 to 16.0 mass%, Cr: 1.0 mass% or less (including 0.0 mass%), V: 0.5 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities.

[0031] 2) WC-TiC-TaC-NbC cemented carbide Co: 5.0 to 20.0 mass%, TiC: 25.0 mass% or less (including 0.0 mass%), TaC: 20.0 mass% or less (including 0.0 mass%), NbC: 15.0 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities. Preferably, Co: 7.0 to 10.0 mass%, TiC: 25.0 mass% or less (including 0.0 mass%), TaC: 10.0 mass% or less (including 0.0 mass%), NbC: 10.0 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities. More preferably, Co: 10.0 to 16.0 mass%, TiC: 20.0 mass% or less (including 0.0 mass%), TaC: 10.0 mass% or less (including 0.0 mass%), NbC: 10.0 mass% or less (including 0.0 mass%), C: 5.0 to 7.0 mass%, the balance being W and inevitable impurities

[0032] (2) Shape The shape of the filler material made of hard alloy is rod-shaped. A rod-shaped wire is one that is difficult to feed from the cylindrical body because it has high rigidity and is difficult to bend. In other words, it is distinguished from a wire-shaped wire that is easy to bend and can be fed from a cylindrical body such as a bobbin. If the hard alloy is rod-shaped, the cross-sectional shape may be, for example, circular, elliptical, or rectangular. The specific shape is determined depending on the shape of the coating layer to be formed, but examples include a circular cross-section with a diameter of 3 to 8 mm and a long length of 1,200 to 2,000 mm.

[0033] (3) Manufacturing Method of Rod-Shaped Hard Alloy Filler Metal For example, a rod-shaped hard alloy filler metal having a sound alloy structure can be manufactured by the following procedure.

[0034] 1) Raw material powder of rod-shaped hard alloy filler material: A raw material powder of rod-shaped hard alloy filler material corresponding to the composition of the hard alloy coating layer is prepared. The raw material powder is WC powder, Cr powder, ３ C ２ Examples of the powder include VC powder, Co powder, TiC powder, TaC powder, NbC powder, TaNbC powder, TiN powder, and NbN powder.

[0035] The raw material powder preferably has an average particle size (Fisher diameter) within a predetermined range. For example, the average particle size (Fisher diameter) of WC powder is 0.5 to 1.5 μm, that of Cr powder is 0.5 to 1.5 μm, and that of Cr powder is 0.5 to 1.5 μm. ３ C ２ The Fischer diameter is measured by a sub-sieve sizer.

[0036] 2) Blending (Mixing) The raw material powders prepared in 1) above are blended to a predetermined blend composition, paraffin wax and ethanol are further added, and the blend is pulverized and mixed in a ball mill for a predetermined time to uniformly disperse the raw material powders, and then dried under reduced pressure.

[0037] 3) Press Molding The mixed powder obtained in 2) above is mixed with a thickener, a surfactant, etc., and molded by injection molding into a green material that will serve as the base for the rod shape after sintering.

[0038] 4) Sintering The green mold body obtained in 3) above is degreased by holding it at 780 to 850°C for 100 to 140 minutes with a temperature increase rate of 0.3 to 1.0°C / min, and subsequently sintered by holding it at a temperature of 1350 to 1450°C for 50 to 70 minutes with a temperature increase rate of 2 to 8°C / min in a vacuum of about 10 to 30 Pa, and then cooled to room temperature at a rate of 5 to 8°C / min in an argon gas atmosphere.

[0039] 5) HIP Treatment The sintered body is heated to 1250-1350°C in an Ar gas atmosphere at a rate of 5-10°C / min, and then subjected to HIP treatment at a pressure of 85-95 MPa for 50-70 minutes, after which it is cooled to room temperature at a rate of 3-10°C / min. A rod-shaped filler metal made of hard alloy is obtained by the HIP treatment.

[0040] 2. Formation of a hard alloy coating layer using a rod-shaped hard alloy filler material The rod-shaped hard alloy filler material produced by the above procedure is used to form a hard alloy coating layer on the surface of a part, for example, using a molding device as outlined in Figure 1 or Figure 2. Figure 1 is a schematic diagram of an example of an apparatus for forming a hard alloy coating layer according to one embodiment of the present invention, and Figure 2 is a schematic diagram of an example of an apparatus for forming a hard alloy coating layer according to another embodiment of the present invention. In Figures 1 and 2, common devices are assigned the same numbers. Note that the molten part of the part and the heat-affected zone (HAZ) are not shown in Figures 1 and 2.

[0041] First, an apparatus for forming a hard alloy coating layer and a method for forming the coating layer using the apparatus will be described, as shown in Figure 1. There are no restrictions on the shape of the portion of the member (1) on which the coating layer is formed, and examples of the cross-sectional shape include a polygon, semicircle, and semiellipse. The feed angle and incident angle described below are defined with the top (apex) of this cross-section as the reference line.

[0042] A rod-shaped hard alloy filler metal (3) heated to its softening temperature by a preheating section (hot wire torch) (2) is fed to a molten pool on the surface of a workpiece (1) by a feeder (not shown). A heat source (4) separate from the preheating section heats the workpiece (1) to form a molten pool (6). The filler metal remains softened and unmelted until it is delivered into the molten pool (6). In the molten pool (6), the hard phase in the rod-shaped hard alloy filler metal (3) remains unmelted, and only the binder phase melts. The hard alloy then naturally cools, forming a hard alloy coating layer (5) on the surface of the workpiece (1). The arrow in Figure 1 indicates the direction in which the coating layer is formed. Note that the molten portion of the workpiece and the heat-affected zone (HAZ) are not shown in Figure 1.

[0043] In the apparatus for forming a hard alloy coating layer shown in Figure 1, the feed angle of the rod-shaped hard alloy filler metal (3) heated to a temperature at which it remains softened and not melted until it is fed into the molten pool (filler metal feed angle) is preferably greater than 4° and less than 75° (more preferably 5 to 60°, even more preferably 7 to 45°, and even more preferably 10 to 35°), and the incident angle of the heat irradiated from the heat source (4) is 3 to 60° (more preferably 4 to 40°, and even more preferably 5 to 35°), with the feed angle being greater than the incident angle. The reason why the feed angle is preferable is that a feed angle exceeding 75° is likely to cause the laser spot to interfere with the hot wire torch used as a preheating zone, which undesirably increases the temperature of the hot wire torch due to the heat effect. On the other hand, a feed angle less than 5° is likely to cause the laser spot to spread in the welding direction, resulting in the formation of an excessive molten pool and resulting in abnormalities such as meandering of the weld bead.

[0044] In the apparatus for forming a hard alloy coating layer shown in FIG. 1, the preheating section (hot wire torch) (2) and the heat source (4) are both provided on the front surface where the coating layer is formed, but at least one of the preheating section (hot wire torch) (2) and the heat source (4) may be provided on the rear surface where the coating layer is formed or on a side surface where the coating layer is not formed.

[0045] Here, the softening temperature of the rod-shaped hard alloy filler material (3) means that the surface temperature of the rod-shaped hard alloy filler material (when W carbide is the base alloy) measured with a radiation thermometer is 1200 to 2000 ° C (preferably 1200 to 1700 ° C).

[0046] In this way, by softening the rod-shaped hard alloy filler metal by the preheating section (2), the hard phase of the rod-shaped hard alloy filler metal does not melt in the molten pool in which the component is melted by heat applied to the component from a heat source (4) provided separately from the preheating section, and only the bonding phase melts, forming a coating layer.

[0047] The preheating section (2) can be exemplified by an electric heating device. The heat source (4) provided separately from the preheating section is not limited as long as it applies heat, and can be exemplified by a laser, electron beam, plasma, arc source, or high-frequency induction heating generator.

[0048] The rod-shaped hard alloy filler material (3) remains in a softened state without melting until it is fed into the molten pool, meaning that the filler material remains in a softened state even when exposed to the irradiated heat, in addition to when it is not exposed to the heat for forming the molten pool, and also means that the filler material remains in a softened state even when the heat of the molten pool is transmitted to the filler material by conduction or radiation, i.e., the surface temperature of the rod-shaped hard alloy filler material (when W carbide is the base alloy) is in the range of 1200 to 2000°C.

[0049] Next, an apparatus for forming a hard alloy coating layer shown in Fig. 2 will be described. The apparatus for forming a hard alloy coating layer shown in Fig. 2 differs from the apparatus for forming a hard alloy coating layer shown in Fig. 1 only in that one roll (7) is provided between the preheating section (2) and above the molten pool (the surface of the roll (7) is separated from the molten pool by a small distance and is not in contact with the molten pool, but because the distance is small, it is difficult to visually recognize this small distance in Fig. 2).

[0050] The apparatus for forming a hard alloy coating layer shown in Figure 2 has one roll (first roll 7), and therefore can form a better hard alloy coating layer than those described below in 1) to 3). Although Figure 2 shows an example using one roll, the number of rolls may be two or more. For example, another roll is arranged to sandwich the filler material. In addition, a third roll is arranged upstream of the second roll on the same side as the first roll.

[0051] 1) The use of the first roll prevents the rod-shaped hard alloy filler from moving in a direction perpendicular to the feed direction, ensuring stable feeding. That is, the first roll presses the rod-shaped hard alloy filler (applying a force with a component perpendicular to the surface of the workpiece, for example, 5 to 200 kPa), allowing the first roll to come into close contact with the rod-shaped hard alloy filler, stabilizing feeding. This more reliably prevents overlap and humping, allowing the feed speed of the rod-shaped hard alloy filler to be increased, and further reducing defects in the appearance of the hard alloy.

[0052] When there are two or more rolls, the roll closest to the molten pool must be above the pool, and tension between the rolls stabilizes the delivery of the rod-shaped hard alloy filler metal.

[0053] 2) Furthermore, if the roll is provided with a caliber into which the cross section of the rod-shaped hard alloy filler metal is inserted, the unstable feeding described above can be further suppressed. In addition, since the outer shape of the rod is formed to the shape of the caliber groove, if the shape of the caliber groove is made to be a preferred shape for the hard alloy coating layer, it is also possible to obtain a hard alloy coating layer in a near net shape (a shape close to the final shape of the hard alloy coating layer).

[0054] 3) The rolls cool the rod-shaped hard alloy filler metal, which can suppress the temperature rise of the rod-shaped hard alloy filler metal before it enters the rolls, and suppress the generation of abnormal phases and coarse carbide particles due to decomposition of carbides in the rod-shaped hard alloy filler metal.

[0055] There are no restrictions on the roll material as long as it satisfies the above 1) to 3). However, the roll closest to the molten pool is preferably made of copper. Furthermore, since the roll is close to the molten pool generated by irradiation from the heat source, its temperature will increase due to the radiant heat from the molten pool, so it is more preferable to use water cooling.

[0056] The thickness of the hard alloy coating layer formed on the component varies depending on the application of the component to which the hard alloy coating layer is applied, but in the case of a die cutter, which is a cutting tool, it is preferable to form it so that it is about 5 mm thick after the subsequent polishing process.

[0057] 3. Post-treatment (polishing) It is preferable that the surface of the hard alloy coating layer is not rough. The allowable surface roughness depends on the application of the member, but for example, for a die cutter, which is a cutting tool, it is preferable that Rz according to ISO 4287-1997 is 0.8 μm or less, and polishing treatment is performed to achieve this surface roughness. For example, polishing treatment can be performed by using different grinding stones to perform rough processing and finish processing.

[0058] 4. Structure of the hard alloy coating layer The hard alloy coating layer consists of a hard phase, a binder phase, a selectively present secondary hard phase, and an abnormal phase. In addition, voids exist within the hard alloy coating layer.

[0059] (1) Hard Phase The hard phase is not particularly limited as long as it can be used as a hard phase of a hard alloy, and may be, for example, W carbide (which may contain W carbide other than WC), a composite nitride of W and Ti, or nitride ceramics (TiN, TaN, NbN, etc.).

[0060] Although there are no particular restrictions on the average diameter of the hard phase, it is more preferable that the circle-equivalent diameter D50 (cumulative 50% diameter: median diameter, D50) is 0.3 to 5.0 μm. When the average diameter of the hard phase satisfies this range, the coating layer has better hardness and toughness. If the average diameter exceeds 5.0 μm, the binder phase also becomes large, resulting in insufficient resistance to plastic deformation and increased wear, which may lead to early deterioration of sharpness when used, for example, as a coating layer for a hard alloy of a cutting tool. If the average diameter is less than 0.3 μm, the toughness is insufficient and early chipping of the cutting tool may occur. The average diameter of the hard phase is more preferably 0.5 to 3.0 μm, and even more preferably 0.6 to 1.5 μm.

[0061] Here, the cumulative 50% diameter (median diameter) refers to the circle-equivalent diameter at which the cumulative percentage is 50% when the horizontal axis is the equivalent circle diameter and the vertical axis is the cumulative percentage of the hard phase relative to the equivalent circle diameter. The number of hard phases on the larger and smaller sides of this cumulative 50% diameter is equal.

[0062] (2) Binder Phase The components and composition of the binder phase are determined according to the components of the hard phase. Examples include binder phases containing Co, Ni, and Fe as the main components.

[0063] The area ratios of the hard phase and binder phase in the coating layer are preferably 50% or more for the hard phase and 40% or less for the binder phase for the following reasons. When the area ratio of the hard phase is less than 50% or the area ratio of the binder phase is greater than 40%, the coating layer has high toughness and is superior in fracture resistance, but its wear resistance is insufficient and it is prone to early wear. Therefore, when used as a coating layer for a cutting tool, for example, cutting performance cannot be maintained for a long period of time. Furthermore, it is even more preferable that the hard phase be 85% or less and the binder phase be 5% or more.

[0064] (3) Secondary Hard Phase Optionally added elements such as Cr, V, etc. constitute a secondary hard phase as a carbide. Since the addition of Cr, V, etc. is optional, the presence of a secondary hard phase is not essential, but when present, it is preferable that the area ratio of the secondary hard phase in the coating layer is 10% or less. This is because if the area ratio of the secondary hard phase exceeds 10%, the secondary hard phase has poor wettability with the binder phase, which makes it more likely for aggregation to occur between the hard phase and the secondary hard phase, resulting in a decrease in the bending strength and a loss of toughness of the coating layer. The area ratio of the secondary hard phase is more preferably 5% or less (it may be 0 area %).

[0065] (4) Abnormal Phase The area ratio of the abnormal phase in the coating layer is preferably 10% or less. The reason for this is that if the area ratio of the abnormal phase exceeds 10%, the probability of the abnormal phase being exposed on the cutting edge of a member polished to a sharp edge increases. In other words, a cutting edge with exposed abnormal phase does not have the wear resistance and toughness required for a cutting edge, and such a cutting edge cannot maintain cutting performance for a long period of time. Since it is preferable that the abnormal phase does not exist, the lower limit of the area ratio of the abnormal phase is 0%.

[0066] Phases that do not fall into the categories of hard phase, binder phase, or secondary hard phase are considered to be abnormal phases. However, as a precaution, we will further explain the phases that are considered to be abnormal phases, including brittle phases, low carbon phases, free carbon phases, and defects in coarse hard phases.

[0067] (4-1) Embrittlement phase The embrittlement phase is W ２ C, M ６ C is W ３ Co ３ C or W ４ Co ２ C, M １２ C is W ６ Co ６ It is composed of one or more of WC. ２ C is hard but brittle and easily broken. ６ C and M １２ Carbon is very brittle and reduces the strength of the hard alloy coating layer.

[0068] (4-2) Low carbon phase The low carbon phase appears due to carbon deficiency or decarburization reaction during the manufacturing process. ６C is W ３ Co ３ C, M １２ C is W ６ Co ６ The low carbon phase is composed of one or more of C. When the low carbon phase is present, the bending strength and compressive strength of the hard alloy coating layer are reduced, which is undesirable.

[0069] (4-3) Free carbon phase The free carbon phase is graphite formed due to an excessive carbon content or due to the decomposition of carbides such as WC, which precipitate independently without bonding with metal elements. The free carbon phase appears due to the addition of excessive carbon or carburization during the manufacturing process, and is undesirable because it reduces the flexural strength and hardness of the hard alloy coating layer.

[0070] (4-4) Coarse hard phases Coarse hard phases are those in which the "phase diameter of the hard phase ≥ the average phase diameter of the hard phase (D50) × 3" is satisfied. The presence of coarse hard phases leads to a decrease in the bending strength of the coating layer. When a member having a hard alloy coating layer formed thereon is used as a cutting tool, it becomes the starting point of fracture. In addition, the presence of coarse hard phases increases the gaps between the hard phases, resulting in coarsening of the binder phase. Areas in which the binder phase has become coarse have reduced resistance to plastic deformation, which leads to rapid wear and a shorter lifespan.

[0071] (5) Voids The presence of voids, i.e., cavities, is undesirable. The reason is that, for example, when a member coated with a hard alloy is a cutting tool, a sharp edge is required at the cutting edge, but if voids exist, they may be exposed at the cutting edge of the polished cutting tool. This is because the exposed voids cause a local decrease in sharpness and lead to poor cutting.

[0072] Here, the area ratio of voids is defined as follows: Area ratio of voids (%) = (area of ​​voids in hard alloy coating layer) / (area of ​​hard alloy coating layer) x 100 Since it is preferable that no voids exist in the hard alloy coating layer, the lower limit of the area ratio of voids is 0%. A method for measuring the area ratio of voids will be described later.

[0073] 5. Vickers Hardness The Vickers hardness of the hard alloy coating layer is preferably 1200 Hv or higher. If the Vickers hardness is less than 1200 Hv, the hard alloy coating layer will have poor wear resistance and be prone to wear. There is no particular upper limit to the Vickers hardness, but according to an example of the manufacturing method described below, the upper limit is approximately 1800 Hv. The Vickers hardness is more preferably 1300 to 1800 Hv, and even more preferably 1400 to 1700 HV. Here, the Vickers hardness is measured under a load of 294 N using the method specified in ISO 6507 or ASTM E385.

[0074] The Vickers hardness (HV) of the coating layer is determined by the grain size of the W carbide and the area ratio of the binder phase, and it is necessary to devise manufacturing conditions to obtain a coating layer with a predetermined Vickers hardness. ３ C ２ and the like, and sintering is performed at an appropriate processing temperature using a W carbide growth suppressor material, and the Fischer diameter of the WC powder used as the raw material is 0.3 to 0.8 μm and the area ratio of the binder phase is 5 to 30%, the Fischer diameter of the WC powder is 0.3 to 1.0 μm and the area ratio of the binder phase is 7 to 35%, or the Fischer diameter of the WC powder used as the raw material is 0.3 to 1.5 μm and the area ratio of the binder phase is 9 to 25%, then the Vickers hardness will be 1200 HV or more.

[0075] 6. Method for identifying each phase and method for measuring the area ratio thereof After identifying the binder phase, secondary hard phase, and hard phase, the area ratio of each of the phases is measured as follows.

[0076] (1) Observation by EDS and EBSD Any cross section or surface of the cemented carbide coating layer is processed to remove any fine irregularities so as to be smooth and not interfere with measurement by an electron backscatter diffraction (EBSD) device. Observation fields are set on the processed surface and observed. The size and number of observation fields may be determined appropriately depending on the specifications of the EBSD device used. The size of the observation fields is set at any position so that each observation field is, for example, 24 μm (vertical) × 72 μm (horizontal). Multiple observation fields (e.g., five or more fields) are set at any position.

[0077] The sample is then observed using a field emission scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and an EBSD measurement device (e.g., OIM Data Collection manufactured by AMETEK). Observation conditions may be determined based on the specifications of the device used. When using the exemplified measurement device, observation is performed at an acceleration voltage of 20 kV, and EBSD patterns and EDS data are simultaneously acquired. The working distance (distance between the lower surface of the objective lens and the sample) is 15 mm, the measurement count rate is 41,000 cps, and the measurement point interval is 50 nm. Measurement points (pixels) are present discretely, but the region (preferably a regular hexagon) extending to the middle between adjacent measurement points is represented by the measurement results of that measurement point. When there is an orientation difference of 5 degrees or more between adjacent measurement points, the region extending to the middle is defined as a crystal grain. However, a measurement point that has an orientation difference of 5 degrees or more from all of its adjacent measurement points, or that exists alone with no adjacent measurement points, is not treated as a crystal grain, and a measurement point is treated as a group of two or more measurement points connected together.

[0078] (2) Identification of each crystal grain For example, measurement data is read into OIM Analysis ver. 7.3.1 manufactured by AMETEK, and for each crystal grain, the EDS count values ​​obtained from each measurement point inside the crystal grain corresponding to each element are averaged to obtain the EDS measurement value of each element in each crystal grain, and the composition of each crystal grain is derived from the obtained measurement value. The details are as follows.

[0079] First, the EDS counts of W, Co, Ni, Fe, Cr, V, Ta, Ti, Nb, and all other elements are averaged over the entire observation field, and then the EDS counts of each element at each pixel inside each grain are averaged to derive the composition of each grain.

[0080] The hard phase is considered to be an aggregate of crystal grains with W as the main component and hcp crystal structure, the binder phase is considered to be an aggregate of crystal grains with Co, Ni, or Fe as the main component and fcc or hcp crystal structure, and the secondary hard phase is considered to be an aggregate of crystal grains with Cr, V, Ta, Ti, Nb, etc. as the main component, and each phase is identified. Phases that do not fall into any of the hard phase, binder phase, or secondary hard phase are considered to be abnormal phases.

[0081] (3) Measurement of the size of hard phases To identify coarse hard phases, the diameter (equivalent circle diameter) of each hard phase is measured and the average diameter (D50) is calculated. Then, as described above, hard phases having an average particle diameter three times or more of this average particle diameter (D50) are treated as coarse hard phases, and the area ratio occupied by the coarse hard phases is measured. Then, this measured area ratio is added to the area ratio of the abnormal phase and subtracted from the area ratio of the hard phase. Here, when calculating the average diameter, it is preferable to measure 300 or more hard phases in order to accurately determine the average diameter.

[0082] 7. Measurement of the Area Percentage of Voids Assuming that voids are uniformly present in the coating layer of the hard alloy, the voids are measured as follows. A sample piece is cut out from the coating layer of the hard alloy and mirror-polished. An observation field of 430 μm × 600 μm is arbitrarily set on the polished sample piece, and the image is observed. The observed image is then binarized so that the voids can be distinguished from the other areas.

[0083] That is, a 256-level gradation display is used, with 0 representing white and 255 representing black, with the lower limit set to 0 and the upper limit set to half the gradation having the most frequent value in the observed image. A threshold is then set using Otsu's binarization process, and the white areas are considered to be voids, and the area ratio of these white areas is measured. As is clear from this measurement method, the area ratio of voids is measured independently of the area ratios of the hard phase, binder phase, etc. that make up the hard alloy coating layer.

[0084] 8. Measurement of the average content of each component The content of each component is measured using an electron probe microanalyzer. A sample for analysis is cut out from the hard alloy coating layer, and three observation fields measuring 96 μm x 128 μm or more are set on the mirror-finished surface (wherein minute irregularities are removed and smoothed so as not to interfere with characteristic X-ray analysis using an electron probe microanalyzer). The components contained and their amounts are measured using characteristic X-rays, and the average of the measurement results is calculated as the content.

[0085] 9. Members Members on which hard alloy coating layers are formed will be described.

[0086] (1) Use and material of member There are no particular restrictions on the member on which the hard alloy coating layer is formed, as long as it has a shape appropriate for the use. Examples of the shape of the member include cutting tools (e.g., die cutters), cutting tools (e.g., end mills), coating devices (e.g., slot dies), and die rolls. There are also no particular restrictions on the material of the member, as long as it is appropriate for the use, and examples of the material include carbon steel, low-alloy steel, stainless steel, and WC cemented carbide.

[0087] (2) Surface Layer A hard alloy coating layer may be formed directly on the surface of a component. Alternatively, a surface layer consisting of one or more layers may be provided on the component, and a hard alloy coating layer may be formed on the surface layer. There are no particular restrictions on the composition of the surface layer, and examples of the surface layer include NCF600, NCF718, and DCoCrC, which are represented by JIS material symbols. The thickness of the surface layer depends on the application, shape, etc. of the component, so it is difficult to discuss its thickness in a uniform manner, but examples include 1 to 5 mm.

[0088] The above description includes the following additional features. (Appendix 1) An apparatus for forming a coating layer on a surface of a component, comprising: a preheating unit that preheats a rod-shaped hard alloy filler metal to a softening temperature; a heat source that applies heat to form a molten pool on the surface of the component; and a feeding unit that feeds the preheated filler metal to the molten pool, wherein the filler metal is fed in a softened state without being melted until it is fed into the molten pool. (Appendix 2) The apparatus for forming a coating layer on a component according to Appendix 1, wherein the feeding unit includes a roll, and the roll is located between an outlet of the preheating unit and above the molten pool. (Appendix 3) The apparatus for forming a coating layer on a component according to Appendix 2, wherein the roll has a pressing unit that applies a pressing force to the softened filler metal in a direction perpendicular to the surface of the component. (Appendix 4) The apparatus for forming a coating layer on a component according to Appendix 2, wherein the feeding unit further includes a second roll. (Appendix 5) The apparatus for forming a coating layer on the surface of any one of Appendices 1 to 4, wherein the preheating unit is an electric heating device. (Appendix 6) The apparatus for forming a coating layer on the surface of any one of Appendices 1 to 5, wherein the heat source that applies heat to form a molten pool on the surface of the component is a generator of any of laser, electron beam, plasma, arc, and high-frequency induction heating. (Appendix 7) The apparatus for forming a coating layer on the surface of a component according to Appendices 1 to 6, wherein the molten pool is formed on a surface layer consisting of one or more layers provided on the surface of the component. (Appendix 8) A method for forming a coating layer on the surface of a component, comprising: providing a rod-shaped filler metal made of hard alloy; softening the rod-shaped filler metal made of hard alloy; generating a molten pool on the surface of the component; and feeding the filler metal in a softened state without melting it until it is fed into the molten pool. (Appendix 9) The method for forming a coating layer on the surface of a component according to appendix 8, characterized in that the rod-shaped filler metal made of a hard alloy is fed into the molten pool while applying a pressing force to the filler metal. (Appendix 10) The method for forming a coating layer on the surface of a component according to appendix 8 or 9, characterized in that the component has a surface layer made of one or more layers on its surface.

[0089] Next, Examples A and B will be described in which a hard alloy coating layer is formed on the cutting edge (12) of the die cutter consisting of the die cut roll (10) and the anvil roll (11) shown in Figure 3 and on the bearer portion (13), but the present invention is not limited to these Examples.

[0090] Example A: A hard alloy coating layer was formed by the following procedure. (1) Raw material powder of rod-shaped hard alloy filler material: WC powder (average particle size (Fisher diameter: the same applies hereinafter): three types of powder with 1.2 μm, 2.3 μm, and 2.9 μm), Cr ３ C ２ Powder (average particle size: 1.4 μm), VC powder (average particle size: 1.5 μm), and Co powder (average particle size: 2.1 μm) were prepared and blended to obtain the blend composition shown in Table 1.

[0091] (2) Blending (Mixing) Next, paraffin wax and ethanol were further added, and the mixture was pulverized and mixed in a ball mill, followed by drying under reduced pressure, thereby obtaining the 10 types of mixed powders shown in Table 1.

[0092] (3) Press Molding A thickener and a surfactant were added to each of these mixed powders, and the mixture was injection molded into a long body that would serve as the base for a rod shape.

[0093] (4) Sintering Each of the long green mold bodies was degreased by holding it at 750°C for 60 minutes with a temperature increase rate of 0.5°C / min, and subsequently sintered by holding it at a temperature of 1360 to 1450°C (sintering temperature listed in Table 1) with a temperature increase rate of 1.7°C / min in a vacuum of 20 Pa for 60 minutes, and the sintered body was cooled to room temperature at 2.9°C / min in an argon gas atmosphere.

[0094] (5) HIP Treatment Next, the sintered body was subjected to HIP treatment in an Ar gas atmosphere, in which the temperature was raised to 1280°C at a temperature rising rate of 4.7°C / min and held at a pressure of 90 MPa for 60 minutes. Thereafter, the sintered body was cooled to room temperature at a cooling rate of 1.2°C / min. The shape of the 10 types of sintered molded bodies that had undergone HIP treatment was a circle with a cross section of 5 mm diameter and a long object of 1500 mm length.

[0095] (6) Coating Using the molding apparatus shown in Figure 1, 10 types of rod-shaped hard alloy filler metals were used to form 5 mm thick hard alloy coating layers on the cutting edge and bearer portion of each die cutter, resulting in die cutters with 10 different hard alloy coating layers (referred to as Examples 1 to 10). The laser output during formation was 3.5 kW, the laser spot size was 2.0 x 6.0 mm, the feed angle of the rod-shaped hard alloy filler metal was 60°, the filler metal feed rate was 0.1 m / min, the laser incident angle was 30°, and the hot wire current was 200 A. The laser was incident on the surface of the workpiece to form a molten pool, and the rod-shaped hard alloy filler metal was fed in a softened state without melting until it was fed into the molten pool.

[0096] (7) Polishing: A grinding process was performed using a grindstone to obtain a cutting edge with a thickness of 3 mm. The Rz was 0.8 μm. The die cutter's die cut roll and anvil roll, both made of SCM440, had a roll diameter of 150 mm and a roll width (distance between bearers) of 230 mm.

[0097] For comparison, die cutters (referred to as Comparative Examples 1 to 5) having five different hard alloy coating layers were obtained by the same process as in the Examples, except that the laser irradiation conditions were changed as described below and the laser was irradiated to both the workpiece and the rod-shaped hard alloy filler material, using the same raw material powder material as in the Examples, except that the laser was irradiated to both the workpiece and the rod-shaped hard alloy filler material.

[0098] (1') Raw material powder for hard alloy coating layer As raw material powder, WC powder (average particle size: 1.5 μm, 2.9 μm, two kinds of powder), Cr ３ C ２Powder (average particle size: 1.4 μm), VC powder (average particle size: 1.5 μm), and Co powder (average particle size: 2.1 μm) were prepared and mixed so that the hard alloy coating layer had the composition shown in Table 1.

[0099] (2') Blending (Mixing) and (3') Pressing Steps Blending (mixing) and pressing steps were carried out in the same manner as in Example.

[0100] (4') Sintering Each long molded body was degreased by holding it at 750°C for 60 minutes with a temperature increase rate of 0.5°C / min, and subsequently sintered in a vacuum of 20 Pa by holding it at a temperature of 1360°C to 1430°C (sintering temperature listed in Table 1) with a temperature increase rate of 1.7°C / min for 60 minutes. The sintered body was cooled to room temperature at 2.9°C / min in an argon gas atmosphere.

[0101] (5') HIP Treatment The same HIP treatment as in the example was carried out to obtain a sintered compact having the same shape as in the example.

[0102] (6') Coating Using the device shown in Figure 1, the laser output was 6.5 kW, the laser spot size was 1.0 x 6.0 mm, the feed angle of the rod-shaped hard alloy filler metal was 70°, the laser incident angle was 50°, and the hot wire current was 400 A. Using five types of rod-shaped hard alloy filler metal, a 5 mm thick hard alloy coating layer was coated on the cutting edge and bearer portion of the die cutter, and five types of die cutters with different hard alloy coating layers (referred to as Comparative Examples 1 to 5) were obtained in the same manner as in Example, except that the laser spot was incident on the workpiece and the rod-shaped hard alloy filler metal.

[0103] (7') Polishing Polishing was carried out in the same manner as in Example.

[0104] The compositions of the hard alloy coating layers of Examples 1 to 10 and Comparative Examples 1 to 5 were measured using an electron beam microanalyzer as described above, and the results are shown in Table 2. Furthermore, the area percentages of the hard phase, binder phase, abnormal phase, and voids obtained by the above-mentioned measurement method for the hard alloy coating layers formed on the die cutter are shown in Table 3. The area percentage of the secondary hard phase was 0.0% in both the Examples and Comparative Examples. Furthermore, the appearance of the coating layer was normal. Note that in Table 3, the abnormal phase was identified by EDS and EBSD, while the voids were identified by image analysis, so the identification methods for the two are different. Furthermore, because the abnormal phase may contain voids, the sum of the area percentages of the hard phase, binder phase, abnormal phase, and voids may exceed 100%.

[0105]

[0106]

[0107] In Tables 1 and 2, "-" indicates that no relevant items were included.

[0108]

[0109] Next, using Examples 1 to 10 and Comparative Examples 1 to 5, a 0.2 mm thick polyester nonwoven fabric was cut. In each Example and Comparative Example, the condition of the cutting edge was checked every 10 minutes (6,000 revolutions) under the following conditions: rotation speed: 600 rpm, pressing force: 2,940 N, cutting edge protrusion: 1.5 μm. When a portion of the material being cut (nonwoven fabric) remained, the cutting edge was considered to have reached the end of its life. The cutting edge was observed, and if there was a missing portion, it was judged to be chipped; otherwise, it was judged to be worn. The results are shown in Table 4.

[0110]

[0111] As is clear from Table 4, the rotational speeds at which the die cutter reaches its end of life are all greater in Examples 1 to 10 than in Comparative Examples 1 to 5, and it is clear that the hard alloy coating layer enhances the durability of the member (die cutter). Furthermore, because this hard alloy coating layer is present only on the cutting edge, it is possible to reduce the amount of raw material powder containing expensive W and Co used.

[0112] Example B In this example, it will be explained that by providing a roll as in the apparatus for forming a hard alloy coating layer shown in FIG. 2, a better hard alloy coating layer can be obtained as described above.

[0113] The hard alloy coating layer was obtained by the following procedure: (1) Raw material powder of rod-shaped hard alloy filler material As the raw material powder of rod-shaped hard alloy filler material (to be the hard alloy coating layer), WC powder (average particle size (Fisher diameter): 1.2 μm), Cr ３ C ２ Co powder (average particle size: 1.4 μm) and Co powder (average particle size: 2.1 μm) were prepared, and the composition was ３ C ２ : 0.9 mass %, WC: the balance.

[0114] (2) Blending (mixing) and (3) Press molding were carried out in the same manner as in Example A.

[0115] (4) Sintering The long green mold body was degreased by heating it at 750°C for 60 minutes at a rate of 0.5°C / min, and then sintered in a vacuum of 20 Pa by heating it at 1380°C for 60 minutes at a rate of 1.7°C / min, and the sintered body was cooled to room temperature at a rate of 2.9°C / min in an argon gas atmosphere.

[0116] (5) HIP Treatment The same procedure as in Example A was carried out to obtain a sintered compact having the same shape as in Example A.

[0117] (6) Coating: Using the hard alloy coating layer forming apparatus shown in Figure 2, a hard alloy coating layer was deposited to a thickness of 5 mm on a rod-shaped hard alloy filler metal. The roll was not calibered. The laser power during welding was 3.5 kW, the laser spot size was 2.0 x 6.0 mm, the filler metal feed angle was 60°, the laser incidence angle was 35°, and the hot wire current was 200 A. The rod-shaped hard alloy filler metal was fed while applying a vertical component force of 150 kPa to the workpiece surface with the roll, resulting in the coated hard alloys of Examples 11 and 12. A molten pool was formed when the laser was irradiated onto the workpiece surface, and the rod-shaped hard alloy filler metal remained softened and not melted until it was fed into the molten pool.

[0118] For comparison, rod-shaped hard alloy filler metals were prepared using the same raw powder materials as those used in Examples 11 and 12. Using the apparatus for forming a hard alloy coating layer shown in Fig. 1 without a roll, the conditions were the same as those for forming a hard alloy coating layer shown in Fig. 2: laser power 3.5 kW, laser spot size 2.0 x 6.0 mm, filler metal feed angle 60°, laser incidence angle 40°, and hot wire current 200 A. The rod-shaped hard alloy filler metal was fed while applying a component force of 150 kPa perpendicular to the workpiece surface using the roll, and the cutting edge was then polished to obtain die cutters (referred to as Examples 13 and 14) with hard alloy coating layers. The laser was irradiated onto the workpiece surface to form a molten pool, and the rod-shaped hard alloy filler metal remained softened and not melted until it was fed into the molten pool.

[0119] The composition of the hard alloy coating layer of Examples 11 to 14 was measured using an electron probe microanalyzer. The appearance of the hard alloy coating layer of all of Examples 11 to 14 was normal, and a problem-free hard alloy coating layer was formed. Here, the composition of the hard alloy coating layer of Examples 11 to 14 is as shown in Table 5, and the feed rate of the rod-shaped hard alloy filler metal is as shown in Table 6. In Table 6, the feed rate of the rod-shaped hard alloy filler metal is referred to as the "filler metal feed rate."

[0120] Table 7 also shows the area percentages of the hard phase, binder phase, abnormal phase, and voids for the hard alloy coating layer formed on the die cutter, measured by the above-mentioned measurement method. The area percentage of the secondary hard phase was 0.0% for both the examples and the comparative examples. Furthermore, the appearance of the coating layer was normal. Note that in Table 7, the abnormal phase was identified by EDS and EBSD, and the voids were identified by image analysis, so the identification methods for the two are different, and the abnormal phase may contain voids, so the sum of the area percentages of the hard phase, binder phase, abnormal phase, and voids may exceed 100%.

[0121]

[0122]

[0123]

[0124] As is clear from Tables 6 and 7, when a rod-shaped hard alloy filler metal is pressed with rolls, even if the feed rate of the rod-shaped hard alloy filler metal ("filler metal feed rate" in Table 6) is increased, the rolls press down the rod-shaped hard alloy, improving adhesion with the workpiece and more reliably reducing the occurrence of overlap and humping. In other words, feeding a rod-shaped hard alloy filler metal while applying pressure with rolls improves productivity.

[0125] The above-disclosed embodiments are merely illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above-disclosed embodiments, and is intended to include any modifications equivalent to the claims and within the scope thereof.

[0126] DESCRIPTION OF SYMBOLS 1 Member 2 Preheating section (hot wire torch) 3 Rod-shaped filler metal made of hard alloy 4 Heat source provided separately from preheating section 5 Hard alloy coating layer 6 Molten pool 7 Roll (first roll) 10 Die-cut roll 11 Anvil roll 12 Cutting edge 13 Bearer

Claims

1. An apparatus for forming a coating layer on a member surface, comprising: a preheating unit for preheating a welding material made of a rod-shaped cemented carbide to a softening temperature; a heat source for applying heat to form a molten pool on the member surface; and a feeding unit for feeding the preheated welding material to the molten pool, wherein the welding material is fed in a softened state without being melted until it is fed into the molten pool. An apparatus for forming a coating layer on a member surface, characterized in that.

2. The apparatus for forming a coating layer on a member surface according to claim 1, wherein the feeding unit includes a roll, and the roll is provided between an outlet of the preheating unit and above the molten pool.

3. The apparatus for forming a coating layer on a member surface according to claim 2, wherein the roll has a pressing portion for applying a pressing force in a direction perpendicular to the surface of the member to the softened welding material.

4. The apparatus for forming a coating layer on a member surface according to claim 2, wherein the feeding unit further has a second roll.

5. The apparatus for forming a coating layer on a member surface according to claim 1 or 2, wherein the member has at least one surface layer, and the molten pool is formed on the at least one surface layer.

6. A method for forming a coating layer on a member surface, comprising: providing a welding material made of a rod-shaped cemented carbide; softening the welding material made of the rod-shaped cemented carbide; heating the member surface to generate a molten pool on the member surface; and feeding the welding material in a softened state without being melted until it is fed into the molten pool. A method for forming a coating layer on a member surface, characterized in that.

7. The method for forming a coating layer on a member surface according to claim 6, wherein the welding material made of the rod-shaped cemented carbide is fed to the molten pool while applying a pressing force to the welding material.

8. The method for forming a coating layer on a member surface according to claim 7, wherein the pressing force is applied by a roll.

9. The method for forming a coating layer on a member surface according to any one of claims 6 to 8, wherein the member has at least one surface layer.

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